The present invention relates to a component part for a musical instrument, such as a side board for forming a body of a grand piano. The component part comprises a plurality of plate-shaped members including a decorated (or fancy) plywood board, and a method for manufacturing such an instrument's component part.
Japanese Patent Application Laid-open Publication No. SHO-63-224902 (hereinafter “Patent Document 1”) discloses a plywood structure and more particularly, a technique for improving the quality of sounds generated from a given sound generating body using the plywood board structure, by adjusting the resonant characteristics of the plywood board through a combination of respective fiber (or grain) directions, materials, etc. of individual plates stuck on top of each other.
Further, Japanese Patent Application Laid-open Publication No. HEI-9-207103 (hereinafter “Patent Document 2”) discloses a method for manufacturing an ordinary type of decorative plywood board. Here, as a step of making a base (plywood) using an upper-layer plate and lower-layer plate with their respective fibers running in their longitudinal directions, the disclosed method includes: severing the upper-layer plate across the width of the plate; positioning and sticking the severed upper-layer plate pieces onto the lower-layer plate in an orientation where the fibers of the plate pieces run in the widthwise direction of the lower-layer plate, to thereby make the base plywood board; and then sticking a decorative veneer sheet (decorative plate) to the top surface of the base plywood board.
Generally, side boards forming the outer peripheral wall surfaces of bodies of grand pianos each comprise a decorative plywood board, which includes a base made of a plurality of plate-shaped wood members joined together end to end in accordance with a necessary length, and a decorative plate stuck on the top surface of the base. Briefly explaining an example of a conventionally-known side board manufacturing method, a first step joins together a plurality of wood plates (veneer sheets) end to end by means of a conventional joint means, such as finger (or combed) joints-,-to-thereby-provide a joined-wood plate unit having an elongated configuration as a whole. The second step adhesively joins, end to end, a plurality of decorative plates having a total length corresponding to the length of the joined wood plate unit, to thereby provide a joined decorative plate unit that has the same length as the joined wood plate unit. Then, a third step sticks a plural number of the wood plate units on top of each other to thereby provide a base plywood board; here, the plural number corresponds to a thickness of a side board to be made. In the third step, it is necessary to position the joined wood plate units, provided by the first step, on top of each other in such a manner that the respective joints (i.e., joined portions between the constituent wood plates) are positionally shifted, in the longitudinal direction, between the individual wood plate units. Namely, because an adhesive is applied to each of the joined portions and the thickness of the joined portion inevitably increases as compared to the remaining portion, the disclosed method attempts to not only deconcentrate or disperse the thickness increases as much as possible and but also minimize a mechanical strength shortage at the joined portions, by positionally shifting the joined portions between the joined wood plate units as noted above.
The fourth step sticks the joined decorative plate unit, provided by the second step, to the base plywood board provided by the third step. The decorative plywood board made in this way is bonded via an adhesive or otherwise after being molded in a mold of a predetermined shape.
Namely, according to the conventional side board manufacturing method, the first step joins together the plurality of wood plates to provide the elongated joined wood plate unit, the second step joins together the plurality of decorative plates to provide the elongated joined decorative plate unit, and then one or more joined wood plate units and the joined decorative plate unit are stuck together. Thus, the conventional manufacturing method requires two joining operations in order to secure the necessary length, which would therefore increase the necessary time and labor. Further, in the conventional manufacturing method, the decorative plates are joined together with their respective end surfaces adhesively bonded with each other merely in an abutting relation in order to make the joints less noticeable. This presents inconveniences in that the joined portions between the decorative plates have a weak joining strength and tend to cause undesired displacement in the thickness direction of the decorative plywood board between the joined decorative plates. Furthermore, for the manufacture of the decorative plywood board, the method requires extra time and labor for positionally shifting the joined portions between the joined wood plate units in the first step.
The method disclosed in Patent Document 2 is basically similar to the above-discussed conventional side board manufacturing method in that a joined decorative plate unit is stuck to the base plywood board, and it does not at all address the problem regarding the number of the joining operations for securing the necessary length and the inconvenience involved in joining the decorative plates together. Patent Document 1 does not particularly discuss a method for manufacturing plywood.